1. Field of the Invention
This invention relates to a method and apparatus for obtaining samples of formation fluids at different levels in a bore hole. The characteristics of formation fluids obtained from various levels within a bore hole are of considerable interest to geologists as an aid to determining subsurface structure as well as to those engaged in well completion and production. This invention provides a method and apparatus for lowering a logging tool into an uncased bore hole on a conventional wireline, positioning the tool at preselected elevations and obtaining formation fluid samples. The samples are tested within the tool without withdrawing it from the bore hole and the test results transmitted to the surface. If it is determined that the sample should be recovered it is transferred to one of a plurality of collection chambers within the tool, and, if not, it is ejected into the bore hole. The logging tool can then be moved to another level, without withdrawal from the well and the process repeated until all of the sample collection chambers in the tool are filled.
2. Description of the Prior Art
Formation fluid sample collection tools have been in use in the industry for a number of years. See for example the descriptive matter found in the Composite Catalog of Oil Field Equipment and Services--1978-1979, pages 3286-3291 for a description of services and equipment provided by Halliburton Services. See also in the 1976-1977 edition of the same catalog the description of the Johnson Inflatable Packer Test Systems at pages 3607-3609. Both the Halliburton and Johnson systems involve attaching the sampling tool to the drill pipe string and are not designed for wireline logging. Moreover, they do not have means for isolating and testing formation fluids at various selected levels within the bore hole to make a determination as to the desirability of collecting and retaining the sample without withdrawal of the tool from the well. These two differences are of considerable significance when the time the well must be out of commission for sampling is taken into consideration. To run a tool into a well on a wireline requires but a small fraction of the time required to run in a drill pipe string and the advantage of being able to collect a number of pretested samples each time the tool is sent down the well further greatly reduces the time during which the well is out of commission.
Wireline formation testers have been available since the early 1950's and have been used to obtain fluids, flow rates and pressures from prospective reservoirs. Because of limited tool capacity and capabilities, however, recovered fluids often are entirely or mostly drilling mud filtrate. Moreover, there is no fluid property monitoring capability. Thus these tools are useful only in the case of reservoirs where adequate flow is obtained and recovered fluids are relatively free of mud filtrate. They tend not to be useful in those cases where geological exploration is involved and fluid samples other than those containing hydrocarbon are desired.